Armor system and method for defeating high energy projectiles that include metal jets

ABSTRACT

An armor system for defeating a solid projectile having an exterior rigid armor plate associated with a fiber-reinforced sheet armor affixed to the interior surface of the exterior armor plate, an interior armor plate, and an inner armor plate displaced from one another to form a first dispersion space between the sheet of self-bonded polymer and the interior armor plate. The first dispersion space is sufficiently thick to allow significant lateral dispersion of armor passing therethrough. The inner armor plate is disposed approximately parallel to the interior armor plate and displaced therefrom to form a second dispersion space between the interior armor plate and the inner armor plate. The second dispersion space is sufficiently thick to allow significant lateral dispersion of materials passing therethrough.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. patent application Ser. No.11/521,307, filed Sep. 15, 2006 entitled, Apparatus For Defeating HighEnergy Projectiles, the content of which is incorporated by referenceherein.

FIELD OF THE INVENTION

The present invention relates to an armor construction that resistspenetration by high energy solid projectiles designed to defeat vehiclearmor.

BACKGROUND OF THE INVENTION

Conventional armor is subjected to a variety of projectiles designed todefeat the armor by either penetrating the armor with a solid orjet-like object or by inducing shock waves in the armor that arereflected in a manner to cause spalling of the armor such that anopening is formed and the penetrator (usually stuck to a portion of thearmor) passes through, or an inner layer of the armor spalls and isprojected at high velocity without physical penetration of the armor.

Some anti-armor weapons are propelled to the outer surface of the armorwhere a shaped charge is exploded to form a generally linear “jet” ofmetal that will penetrate solid armor; these are often called HollowCharge (HC) weapons. A second type of anti-armor weapon uses a linear,heavy metal penetrator projected at high velocity to penetrate thearmor. This type of weapon is referred to as EFP (explosive formedprojectile) or SFF (self forming fragment) or a “pie charge” orsometimes a “plate charge.”

In some of these weapons the warhead behaves as a hybrid of the HC andthe EFP and produces a series of metal penetrators projected in linetowards the target. Such a weapon will be referred to herein as a Hybridwarhead. Hybrid warheads behave according to how much “jetting” or HCeffect it has and up to how much of a single big penetrator-like an EFPit produces.

Various protection systems are effective at defeating HC jets. Amongstdifferent systems the best known are reactive armors that use explosivesin the protection layers that detonate on being hit to break up most ofthe HC jet before it penetrates the target. The problem is that theseexplosive systems are poor at defeating EFP or Hybrid systems

Another system has been proposed to defeat such weapons where the armoris comprised of two layers with an electrical conductor disposedtherebetween. An significant electric potential is created between theelectrical conductor and the adjacent surfaces of the armor. When a jetor elongated solid penetrator penetrates the armor it creates anelectrically conductive path between the armor layers and the electricalconductor through which the electrical potential is discharged. Whenthere is sufficient electrical energy discharged through the penetratorit is melted or vaporized and its ability to penetrate the next layer ofarmor is significantly reduced.

Another type of anti-armor weapon propels a relatively large, heavy,generally ball-shaped solid projectile (or a series of multipleprojectiles) at high velocity. When the ball-shaped metal projectile(s)hits the armor the impact induces shock waves that reflect in a mannersuch that a plug-like portion of the armor is sheared from thesurrounding material and is projected along the path of the metalprojectile(s), with the metal projectile(s) attached thereto. Such anoccurrence can, obviously, have very significant detrimental effects onthe systems and personnel within a vehicle having its armor defeated insuch a manner.

While the HC type weapons involve design features and materials thatdictate they be manufactured by an entity having technical expertise,the later type of weapons (EFP and Hybrid) can be constructed frommaterials readily available in a combat area. For that reason, and thefact such weapons are effective, has proved troublesome to vehiclesusing conventional armor.

The penetration performance for the three mentioned types of warheads isnormally described as the ability to penetrate a solid amount of RHA(Rolled Homogeneous Armor) steel armor. Performances typical for theweapon types are: HC warheads may penetrate 1 to 3 ft thickness of RHA,EFP warheads may penetrate 1 to 6 inches of RHA, and Hybrids warheadsmay penetrate 2 to 12 Inches thick RHA. These estimates are based on thewarheads weighing less than 15 lbs and fired at their best respectiveoptimum stand off distances. The diameter of the holes made through thefirst inch of RHA would be; HC up to an inch diameter hole, EFP up to a9 inch diameter hole, and Hybrids somewhere in between. The bestrespective optimum stand off distances for the different charges are:standoff distances for an HC charge is good under 3 feet but at 10 ft ormore it is very poor; for an EFP charge a stand off distance up to 30feet produces almost the same (good) penetration and will only fall offsignificantly at very large distances like 50 yards; and for Hybridcharges penetration is good at standoff distances up to 10 ft but after20 feet penetration starts falling off significantly. The way thesecharges are used are determined by these stand off distances and themanner in which their effectiveness is optimized (e.g., the angles ofthe trajectory of the penetrator to the armor). These factors effect thedesign of the protection armor.

The present invention is effective against Hybrid charges because itmust be placed close to the edge of the road to provide deep penetrationand thus it must be angled upward to hit the desired portion of thetarget. As a result it does not hit the armor at a right angle to itssurface. The jet is therefore at least partially deflected from itstrajectory and its penetration is reduced. An effective EFP can hit froma relatively long stand off distance and has a good chance of hittingsquare on with good penetration but the present invention is veryeffective against EFPs. The Hybrid and EFP are the threats the inventionis intended to address.

While any anti-armor projectile can be defeated by armor of sufficientstrength and thickness, extra armor thickness is heavy and expensive,adds weight to any armored vehicle using it which, in turn placesgreater strain on the vehicle engine, and drive train.

Armor solutions that offer a weight advantage against these types ofweapons can be measured in how much weight of RHA it saves when comparedwith the RHA needed to stop a particular weapon penetrating. Thisadvantage can be calculated as a protection ratio, the ratio being equalto the weight of RHA required to stop the weapon penetrating, divided bythe weight of the proposed armor system that will stop the same weapon.Such weights are calculated per unit frontal area presented in thedirection of the anticipated trajectory of the weapon.

Thus, there exists a need for an armor that can defeat the projectilesfrom anti-armor devices without requiring excess thicknesses of armor.Preferably, such armor would be made of material that can be readilyfabricated and incorporated into a vehicle design at a reasonable cost,and even more preferably, can be added to existing vehicles.

As the threats against armored vehicles increase and become morediverse, combinations of armor or armor systems are needed to defeat thevarious threats. The present invention is in addition to the commondesign features needed to protect the vehicle against military assaultrifle bullets, bomb shrapnel and landmine explosions. An armor systemthat raises the protection level of an armored vehicle to include EFPand Hybrid charges is described.

SUMMARY OF THE INVENTION

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

To achieve the objects and in accordance with the purpose of theinvention, as embodied and broadly described herein, the inventioncomprises an armor system for defeating a solid projectile. The systemincludes an exterior rigid armor plate having an exterior surface and aninterior surface. A fiber-reinforced sheet armor, comprised of aplurality of fibers having an ultimate tensile strength greater than3GPa bonded to form the sheet by a polymer surrounding the fibers isaffixed to the interior surface of the exterior armor plate. The systemfurther includes an interior armor plate disposed approximately parallelto the fiber-reinforced sheet armor. An inner armor plate is disposedapproximately parallel to the interior armor plate and is displacedtherefrom to form a second dispersion space between the interior armorplate and the inner armor plate. The second dispersion space issufficiently thick to allow significant lateral dispersion of materialspassing therethrough.

An embodiment of the invention is an armor system for defeating a solidprojectile where the fiber in the fiber-reinforced sheet armor sheetconsists essentially of a material selected from the group consistingof: poly-paraphenylene terephthalamide, stretch-oriented high densitypolyethylene, stretch-oriented high density polyester, a polymer basedon pyridobisimidazole, and silicate glass.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of theinvention and together with the description, serve to explain theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of the present invention;

FIGS. 2A-B are schematic, cross-sectional views of one embodiment of theinvention being challenged by a relatively heavy, non-elongated solidprojectile preceded by an elongated metal jet;

FIG. 3 is a perspective view of one embodiment of the present inventionwhere the exterior armor plate has a plurality of projections on theouter surface;

FIG. 4 is a perspective view of one embodiment of the present inventionwhere the first dispersion space contains a plurality of dispersioninducing members, embodied here as glass spheres;

FIG. 5 is a cross-sectional view of an embodiment of the invention wherethe armor comprising the body of the vehicle is the inner armor plate ofthe invention;

FIG. 6 is a schematic cross-sectional view of an embodiment of theinvention where the armor comprising the body of the vehicle is theinner armor plate of the invention and the vehicle includes an interiorprojectile absorbing layer inside the body;

FIG. 7 is a schematic cross-sectional view of an embodiment of theinvention where the armor comprising the body of the vehicle is theinner armor plate of the invention and the vehicle includes an interiorprojectile absorbing layer inside the body of fabric and ceramic plateson the interior surface of the vehicle body;

FIG. 8 is a schematic cross-sectional view of an embodiment of theinvention where the armor comprising the body of the vehicle is theinner armor plate of the invention and the vehicle includes an interiorprojectile absorbing layer inside the body of fabric and ceramic platesspaced from the interior surface of the body to form a gap; and

FIG. 9 is a perspective view of one embodiment of the present inventionwhere there is an electrically conductive sheet between the layeredarmor plates and a source of electrical power disposed to apply suchpower to adjacent conductive layers in the armor system.

FIG. 10 is a perspective view of another embodiment of the presentinvention where there is an electrically conductive sheet between thelayered armor plates and an associated power source.

FIG. 11 is a perspective view of still another embodiment of the presentinvention where there is an electrically conductive sheet between thelayered armor plates and an associated power source.

FIG. 12 is a perspective view of still another embodiment of the presentinvention where there is an electrically conductive sheet between thelayered armor plates and an associated power source.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

In accordance with the invention, there is provided an armor system fordefeating a solid projectile. While the invention and its embodimentsmay impede penetration relatively, non-elongated, heavy, solid metalprojectiles formed and propelled by either manufactured explosivedevices or improvised explosive, its primary utility is to defeatdevices of elongated metal “jets” produced by shape charges along withthe heavy solid projectiles. The parameters of the system can beselected to defeat a particular projectile if its weight, density,velocity, and size are known. The parameters of the system are themechanical properties (ultimate tensile strength, hardness, elasticmodulus, fracture toughness, and velocity of forced shock) of the layersof material comprising the layers of the invention, the spacing of thelayers (the distance between layers, i.e. the thickness of thedispersion space) and the nature of any materials placed in the spacebetween the layers.

Some embodiments of the invention have a plurality of projections on theinner surface of at least one armor plate in the system. The purpose ofthe plurality of projections on the inner surface is to disperse solidprojectiles erupting through the inner surface of the plate. Themechanism by which the inner surface induces dispersion of materials maynot be the same as that of projections on a surface on which theprojectile impinges but, irrespective of the mechanism, the projectionson the inner surface disperse the material erupting therefrom and indoing so achieves one of the objectives of the system. The shockwavespassing through the system provide the energy for the eruption at theinner surface of the plate but the direction of the eruption is dictatedby the shape of the inner surface of the material with the shockwaveenergy in it and the material adjacent the inner surface into which theshock energy is to be transmitted. When the material receiving the shockenergy from the solid has a significantly lower velocity of transmissionof a forced shock wave the energy will be reflected at the surface andnot transmitted. For example, where the material with the shock wave init is a solid (e.g., aluminum or steel that conduct shockwaves at 5000meters/sec.) and the material receiving the shock wave is air (having avelocity of transmission of a forced shock wave of only 330 meters/sec.)the mismatch will cause the energy to build up at the plate surfaceinvolved and then cause an eruption. One form of such an eruption isknown as spalling

The material properties of the solid material forming the plates effectthe dissipation of energy and transmission of momentum away from thepenetration line and thereby effect how spalling occurs at the rear ofthe metal plates. If the material is brittle (like with most ceramics)the hardness advantage at the front face is lost at the rear face wherethe spalling occurs because the material has a very low elongation tobreak and the material breaks into small pieces carrying less energy offthe line of penetration. A large single spall can develop in materialslike steels and other metals when they exhibit a value for elongation tobreak of 10% or more. A material with a high tensile strength (like morethan 30,000 lbs./in.² for aluminum) coupled to a high elongation valuerequires a larger amount of energy to tear loose a large spall. A heavyspall relative to the mass of the striking projectile will, through thelaws of conservation of momentum, result in a larger drop in velocity ofthe components exiting rear of the plate and being carried across thedispersion space onto the next protection plate.

Where the system contains a layer of fibrous material at or near theoutermost layer of the armor system, the fibrous layer attenuates theenergy of the penetrating material by resisting the enlargement of anopening therein by virtue of the extremely high tensile strengths of thefibers comprising the fibrous sheet. Even if penetrated by an elongatedpenetrator, the initial opening resists enlargement and exerts highshear forces on the lateral surfaces of the elongated penetrator. Thisslows the penetrator and reduces the energy in the penetrator. Thisincreases the probability that the next layer in the armor system willeither defeat the penetrator, or further slow the penetrator such thatlayers of the system that will encounter the penetrator may have abetter chance of defeating it.

As will be disclosed in more detail below, the system is comprised of aplurality of layered plates separated by what is termed a dispersionspace. In some embodiments projections from the outer or inner surfaceused to induce dispersion of the material impinging on or erupting froma surface can be used on any one of the plates in the system on bothopposing surfaces, the outermost surface, the innermost surface, or notat all.

In another embodiment, where the trajectory of the projectile (and henceits expected line of penetration) is known, the armor plate may beangled so that the line of penetration is no longer perpendicular to theouter surface. In such an embodiment at least one of the armor platesare inclined with respect to the anticipated trajectory of theprojectile. It is preferred that each of the plates be inclined at anangle of 20° or more with respect to the anticipated trajectory of theprojectile.

In accordance with the invention there is provided an exterior rigidarmor plate having an exterior surface and an interior surface. Theplate may have parallel, opposing flat surfaces, or in certainembodiments the surface of the plate on which a projectile would firstimpinge (the “outer” surface) may include a plurality of projections onthe outer surface. The projections are disposed to at least partiallyfragment solid projectiles impinging on the outer surface of the plate.The size and configuration of the projections are determined by theproperties of the projectile and the material forming the plate. It isnot the purpose of the projections on the outer surface of the firstplate to defeat the projectile but to deflect an elongated “jet” ofmetal moving at high velocity in front of a relatively heavy projectilemoving at a lower velocity along the same trajectory. Such a penetratoris characteristic of what is termed herein as a Hybrid weapon. As willbe disclosed further, the primary goal of the invention is to inducedispersion of the projectile as it passes through the armor system. Whatis meant by dispersion is the deflection of portions of the projectileand any portions of the material forming layers in the system from theinitial trajectory of the projectile.

The outer armor layer may consist essentially of a sintered materialselected from the group consisting of: silicon carbide, boron carbide,alumina, and a blend of zirconia and alumina. One embodiment of thepresent invention includes a ceramic outer armor layer of CeraShield™ceramics, products of the CoorsTek® Armor, Group CoorsTek, Inc., 16000Table Mountain Parkway, Golden, Colo., 80403. Other preferredembodiments include metals including steel, aluminum alloys, andtitanium alloys.

In accordance with the invention there is provided a fiber-reinforcedsheet armor affixed to the interior surface of the exterior armor plate.The fiber-reinforced sheet armor is comprised of a plurality of fibershaving an ultimate tensile strength greater than 2.5 GPa bonded to formthe sheet by a polymer surrounding the fibers. Without being bound bytheory it is believed that any jet of material penetrating the fibrouslayer must separate the fibers laterally and hence apply a tensile loadon the fibers. When the fibers are sufficiently strong (have a hightensile strength), the material surrounding the jet constricts the jetand slows it substantially. Because the jet defeats armor by the inertiaof an elongated (explosive formed) penetrator, the reduction of thevelocity of the jet significantly reduces its effectiveness. Because thefibrous layer is one of the first of several layers of armor in thesystem of the present invention, the latter layers can more readilydefeat the jet.

Recent developments in fiber technology have created fibers havingtensile strengths in relatively light materials that are in excess of3GPa. In a preferred embodiment the fiber in the fiber-reinforced sheetarmor consists essentially of a material selected from the groupconsisting of: poly-paraphenylene terephthalamide, stretch-oriented highdensity polyethylene, stretch-oriented high density polyester, a polymerbased on pyridobisimidazole, and silicate glass.

Preferrably the fiber-reinforced sheet armor sheet consists essentiallyof a sheet of stretch-oriented, high molecular weight polyethylenes,especially linear polyethylenes, having an ultrahigh molecular weight of600,000 to 6,000,000 g/mol and higher. Such fibers are bound together toform a sheet-like product with a polymeric matrix materials, for examplethermosetting resins such as phenolic resins, epoxy resins, vinyl esterresins, polyester resins, acrylate resins and the like, or polarthermoplastic matrix materials such as polymethyl (meth)acrylate. Aparticularly preferred fiber-reinforced sheet armor of this type isknown commercially as Dyneema®, a product of DSM Dyneema, Mauritslaan49, Urmond, P.O. Box 1163, 6160 BD Geleen, the Netherlands.

Another preferred fiber-reinforced sheet armor sheet consistsessentially of a composite panel made of high molecular weightpolypropylene. In such a product tape yarn of high molecular weightpolypropylene is woven into a fabric. Multiple layers of fabric arestacked and consolidated with heat and pressure to form rigid sheetsusing low molecular weight polypropylene as a matrix. A particularlypreferred fiber-reinforced sheet armor made of this type material isknown commercially as MTF sheet, a product of Milliken & Company, 920,Milliken Road, P.O. Box 1926, Spartansburg, S.C., 29303 USA.

As here embodied, and depicted schematically in FIG. 1, there is aseries of generally parallel plates 10, comprised of an outer armorplate 12, a fibrous outer armor plate 12′, an interior armor plate 14,and an inner armor plate 15. In the embodiment depicted the fibrousarmor plate 12′ is bonded to the outer armor plate 12 on the interiorsurface 13 of the armor plate 12. In other embodiments a mechanicalfastening can be used to join the fibrous armor plate 12′ to the outerarmor plate 12 or the fibrous armor plate 12′ be confined between toadjacent armor plates with no dispersion space (not shown). In thisembodiment the outer surface 11 of the armor plate 12 is planar.

As used herein “armor plate” is a plate-like member disposed tofragment, deflect, or disperse a projectile or absorb energy from theprojectile to facilitate its defeat by other portions of the system. Itmay be a know armor plate material (i.e. a metal plate of highstrength), a conventional metal plate of lower strength thanconventional armor plate, or a sheet-like member of fibrous materialthat is used in the present invention to affect a projectile such thatother elements in the armor system defeat the projectile. In a preferredembodiment the inner armor plate 15 may comprise the body of an armoredvehicle.

As here embodied and depicted in FIG. 1, the system includes a firstdispersion space 18, separating plates 12′ and 14 a distance 19, asecond dispersion space 20, with the outer surface of the series ofplates 10 being surface 11 of plate 12.

In accordance with the invention, the series of plates are separated bya dispersion space. As noted above, a dispersion space is the spacebetween adjacent plates and it is the function of the dispersion spaceto allow lateral dispersion of material passing therethrough. The termlateral means in a direction at an angle from the initial line of flightof the projectile, i.e. its trajectory. The more the moving material isdispersed the less concentrated is the energy impinged on the nextsuccessive layer. In addition, the greater the distance between layers(the greater the thickness of the dispersion space) the less kineticenergy per surface area will be possessed by the moving material.Clearly if the dispersion distance is very large, large amounts ofkinetic energy will be spread out from the original penetration line andlost, but the resulting layered structure will be impractically thick.On the other hand, if the thickness of the dispersion space is too smallthe moving material is not dispersed, its kinetic energy and momentum isnot dissipated, and it may have sufficient energy and concentration todefeat subsequent layers of the system. One skilled in the art to whichthe invention pertains, with the general guidance provided herein, incombination with the example below can devise a system to defeat aparticular projectile or mix of projectiles traveling at a particularvelocity along a particular trajectory.

In a preferred embodiment of the invention the first armor layer is arelatively thin, hard material on its outer surface, e.g., a layer ofceramic material, to induce fracture and or deformation of theprojectile. In this embodiment the function of the first armor layer isto absorb some of the energy of the projectile, to flatten it (laterallydisplace at least some of its mass) and to significantly reduce itsvelocity. The adjacent fibrous armor layer 12′ absorbs energy from theprojectile and reduces its velocity.

The weapon against which the present invention has particular utility isdepicted in FIGS. 2A and 2B. In those figures a projectile 16 has beenformed by an explosive device to have a relatively heavy and slow movingportion 16′. Ahead of the portion 16′ is an elongated “jet” of materialmoving at a higher velocity along the same trajectory. As disclosedpreviously, because the jet is moving at a high velocity and has arelatively small cross-sectional area, it poses a significant threat toarmor systems. This is especially true because shortly after the jetencounters a target (and has whatever effect on that target such a jetmay have) the same portion of the target receives a relatively largeshock from the heavy portion 16′ of the projectile at the same locationthat encountered the jet.

FIG. 2B depicts an embodiment of the invention after the jet haspenetrated the outer armor plate 12 and the inner plate 12″ before therelatively heavy portion of the projectile 16′ has imparted its energyto the armor system. At this time the constriction effect of the fibrousouter plate has slowed the jet portion 16″ and even though the outerarmor layer 12 and the fibrous outer plate 12′ have been breached, theenergy absorbed by the fibrous layer 12′ and the energy that will beabsorbed by the portion 16′ of the projectile 16 fracturing the outerarmor plate 12 and deforming and possibly fracturing the fibrous outerplate 12′ will significantly attenuate the energy in the projectile 16.This significantly increases the probability that the projectile 16 willbe defeated by the remaining portions of the armor system, as hereembodied, layers 14 and 16.

It is further preferred that the velocity of shockwaves in the armorplate should be significantly faster than the velocity of thepenetrator. The toughness of the armor plate can then be brought to bearand the tear line can, by reflection and resonance, give a favorabletear line depicted in FIG. 2B as angle α. The larger the angle α, themore energy is absorbed in the deformation of the plate beingpenetrated, and the larger the combined weight of the penetrator and theportion of the armor adherent to it.

The velocity of forced shockwaves in steels and aluminum alloy plates isabout 5,000 meters/sec., so if the striking projectile has a velocityclose to or higher than that the penetration would behave more like anHC. The penetration of an HC depends on the density of the material itis penetrating and lower density materials perform better. When dealingwith high velocity strikes aluminum armor is preferable to steel armorbut when the velocity has been reduced by preceding penetrations thentough steel plates also become effective. EFP normally have a velocityof 2,500 meters/sec. or slower and Hybrids have the smaller and lighterleading penetrators moving at 3,000 to 3,500 meters/sec. so they aremore difficult to stop.

Once the penetrator 16″ and the relatively heaving projectile portion16′ have been slowed and basically deformed into one projectile, theprojectile penetrates or shears plates in a manner that can bepredicted. The relationship of the mass and velocity of the projectileconforms to a conservation of momentum relationship of:M_(p)·V_(p)=(M_(p)+M_(s))·(V_(p&s)), where M_(p) is the mass of theprojectile, V_(p) is the velocity of the projectile at impact, M_(s) isthe mass of the sheared portion of the plate and V_(p&s) is the velocityof the combined projectile and sheared portion of the plate.

In a preferred embodiment, the first dispersion space is sufficientlythick to allow significant lateral dispersion of material passing thoughthe first dispersion space. As here embodied in a system comprised of aseries of armor plates shown in FIG. 1, the first dispersion space 18has a sufficient thickness (as indicated by arrow 19) to allowsignificant lateral dispersion of material (the projectile and portionsof the plate 12.

In a preferred embodiment the interior armor plate 14 and the innerarmor plate 15 have an ultimate tensile strength of 50,000 lbs./in.² forsteel plates and 30,000 lbs./in.² for aluminum. Preferably such a layerwill have an elongation at tensile rupture of greater than 10%. Whenthese armor layers have a high fracture toughness the mass of thematerial penetrating the outer layer may increase, but its velocitydecreases and the material is laterally dispersed.

Where the armor plates 14 and 15 are an aluminum alloy it is preferredthat they consist essentially of an aluminum alloy having an elongationat fracture of at least 7% and more preferably 10%. Examples ofpreferred aluminum alloys include: 7017, 7178-T6, 7039 T-64, 7079-T6,7075-T6 and T651, 5083-0, 5083-H113, 5050 H116, and 6061-T6. When thearmor layer consists essentially of an aluminum alloy it is preferredthat it have a thickness in the range of from 8 to 40 millimeters. Wherethe armor plates 14 and 15 are steel it is preferred that such platesconsist essentially of material having an elongation at fracture of atleast 7% and more preferably 10%. Examples of preferred steels include:SSAB Weldox 700, SSAB Armox 500T (products of SSAB Oxelösund ofOxelösund, Sweden), ROQ-TUF, ROQ-TUF AM700 (products of Mittal Steel,East Chicago, Ind., USA), ASTM A517, and steels that meet U.S. Militaryspecification MIL-46100. When the armor layer consists essentially ofsteel it is preferred that it have a thickness in the range of from 5 to20 millimeters.

In another preferred embodiment the surface or surfaces of at least oneof the armor plates is configured to induce fragmentation of theprojectile and the material being penetrated by the projectile.

As here embodied, and depicted in FIG. 3, the outer surface 11 of thearmor plate 12 includes a plurality of projections 28. The projectionsdepicted in FIG. 3 are pyramidal, but the configuration of theprojections is not known to be critical. The projections 28 are disposedto at least partially fragment solid projectiles impinging on the outersurface of the armor plate and induce as much lateral fragmenting of thematerial being penetrated as can be induced without the reducedthickness caused by the grooves 30 reducing the strength of the armorplate. It is also preferred that at least one of the armor plates in thearmor system have an inner surface facing a dispersion space thatincludes a plurality of projections. In this embodiment the projectionsare disposed to disperse the solid material erupting through the innersurface of the armor plate by inducing lateral fracture of thepenetrated layer. While the outermost armor layer of this embodiment hasprojections only from its outer surface, the interior armor plates mayhave projections on both. Due to the fragmentation of the layer andprojectile the impact on the next adjacent plate will be a plurality ofseparate impacts that are dispersed over a wider area and the next platereceiving such materials will better resist penetration and ifpenetrated will more likely fracture in pieces.

Another embodiment of the invention also induces lateral dispersion ofmaterial passing through the dispersion spaces in the layered device byplacing dispersion elements in the dispersion space. At very highvelocity impact conditions the induced forced shockwaves transmittedinto the dispersion elements carry a large percentage of the energyexerted on the dispersion elements by the penetrator. The dispersionelements are then launched by this energy as a spall or the objectcontaining the shock energy must pass the energy on to another receiver.

As here embodied and depicted in FIG. 4, the system 10 includes aplurality of spheres 34 located in the first dispersion space 18 betweenarmor layers 12′ and 14. The spheres may consist essentially of amaterial selected from the group consisting of brittle metal, ceramic,and glass. When the dispersion elements are surrounded by a liquid orgel that is able to conduct shock away, then the dispersion element inturn can accept more shockwave energy without shattering or being movedout of the path of the penetrator. As here embodied the system 10includes a gel 35 surrounding the spheres 34. One embodiment may usecombinations of materials with complimentary forced shockwaveproperties. Examples are spheres of glass or ceramics in which typicallythe speed of shock energy moves at more than 5,000 meters/sec.surrounded by a liquid like water (1,500 meters/sec.) or glycerin (1,800meters/sec.) or glycol (1,800 meters/sec.) or mixtures of these liquids.The liquids can be gelled by a gelling agent like gelatin or fusedsilica, fused silica, potassiumpolyacrylate-polyacrylamide copolymers orsimilar organic polymer gel agents.

In accordance with the invention there is provided an inner armor platedisposed approximately parallel to a separate armor plate and displacedtherefrom to form a second dispersion space between the separate armorplate and the inner armor plate, the second dispersion space beingsufficiently thick to allow significant lateral dispersion of materialspassing therethrough.

As here embodied and depicted in FIG. 1 the system includes an innerarmor plate 15. As disclosed above, the primary purpose of the innerarmor plate is to prevent any further penetration of material that hasbeen dispersed and slowed by passage through the upper portions of thesystem, i.e., the outermost armor plate(s) and dispersion space(s). Theembodiment depicted includes three plates but the inventions is notlimited to that number of plates, hence reference in the disclosure tothe “inner” armor plate adjacent the inner armor plate. Thus, theinvention may include more than three armor plates, and it is stillpreferred that the inner armor plate be comprised of a material of highfracture toughness to resist any further penetration by materialimpinged thereon.

It is preferred that the inner plate be comprised of a material that hasa Brinell hardness in excess of 350. It is further preferred that theinner plate consist essentially of a material selected from the groupconsisting of: an aluminum alloy, a steel alloy, and a titanium alloy, ametal matrix composite, and a polymer matrix composite. As has beenrepeatedly disclosed, one of the primary goals of the system is toinduce dispersion of the material passing through the armor system toimprove the probability that such material will not penetrate thesystem.

Another embodiment of the invention is the incorporation of an armorsystem on an existing vehicle, armored or unarmored. For an unarmoredvehicle the inner armor plate should resist penetration of any materialpassing through the armor system so the material does not enter thevehicle. In that way the ability of an unarmored vehicle to surviveattack by armor-piercing munitions or devices is significantly improved.Armored vehicles can have their resistance to attack by armor-piercingmunitions or devices is further improved by the incorporation of thepresent invention on the exterior surface of the armored vehicle.

An embodiment of an armored vehicle having its penetration resistanceimproved is depicted in FIG. 5, a schematic cross-sectional view of ablast-resistant armored land vehicle 36 having a monocoque body 38comprised of sheet armor. In this embodiment the body 38 has a bottomportion 40 defining at least one V, with the apex of the V substantiallyparallel to the centerline of the vehicle. In this embodiment the armorsystem of the present invention is affixed to the exterior of thearmored vehicle and the inner armor layer of the armor system of theinvention comprises the sheet armor body of the vehicle.

An alternative embodiment would be a separate assembly of layered armorplates added to an existing vehicle, or portions of the vehicle, toenhance its resistance to the weapons described above.

In a preferred embodiment the interior layer of armor comprises the bodyof a vehicle. In the embodiment depicted in FIG. 5 the sheet materialused to form the interior layer 16 of the body 38 may be at least twodifferent sheet materials. In the embodiment depicted the portion of thebody 16 that comprises the V-shaped portion 42, here a “double-chined”V, may be formed of a tough sheet material. As used herein the word“tough” is a material that resists the propagation of a cracktherethough, generally referred to as a material that has a highfracture toughness. As here embodied the portion of the interior layerof the body 16 that comprises the bottom portion 40 (comprising the Vshaped portion 42) is preferably sheet steel known as “ROQ-tuf AM700 (aproduct of Mittal Steel, East Chicago, Ind.). Another material known asSSAB Weldox 700 (a product of SSAB Oxelösund of Oxelösund, Sweden) isalso preferred as the material for the bottom portion 40. Steelsnormally used for the construction of boilers like A517, A514 and othersteels having similar yield strengths and elongation to break comparableto ROQ-tuf and Weldox 700 may also be used. The upper portion 44 of theinterior layer 16 of the body 38 is preferably formed of armor plate. Aparticularly preferred material is known as SSAB Armox 400 (a product ofSSAB Oxelösund of Oxelösund, Sweden), although an armor meeting U.S.MIL-A-46100 will be operable. Generally, the sheet material for layer 16preferably consists essentially of a metal selected from the groupconsisting of: steel, steel armor, titanium alloys, and aluminum alloys.In this preferred embodiment there is an interior armor layer 14 and twoouter layers 12 and 12′. Preferably, the outer armor layer 12 consistsessentially of a sintered material selected from the group consistingof: silicon carbide, boron carbide, alumina, and a blend of zirconia andalumina and a fiber-reinforced sheet armor 12′ affixed to the interiorsurface of the exterior armor plate. The fiber-reinforced sheet armor12′ is comprised of a plurality of fibers having an ultimate tensilestrength greater than 2.5 GPa bonded to form the sheet by a polymersurrounding the fibers. The preferred composition of the layer 14 hasbeen disclosed above. T

In a further preferred embodiment the vehicle body includes a layer ofsheet armor 46 adjacent the interior surface of the body. As hereembodied, and depicted in FIG. 6, the system includes outer armor layers12 and 12′, inner armor layer 14 and interior armor layer 15. The bodyof the vehicle, here 16 also has a layer of sheet armor 46 adjacent theinterior surface of the body. In a further preferred embodiment, thissheet armor 46 comprises a rigid polymer/fiber composite.

The sheet armor 46 may also comprise a woven fabric comprised of fiber.A still further preferred embodiment includes an interior layer of armorof woven fabric 46′ comprised of fiber and a plurality of ceramic plates48, as schematically depicted in FIG. 7.

In another embodiment, depicted in FIG. 8 the fibrous sheet armor 46′(or the rigid polymer/fiber composite 46, or another layer of metalarmor plate (not shown)) adjacent the interior surface of the body 38 isspaced from the interior surface to form a gap 50.

While the present invention provides resistance to solid projectiles, italso provides an opportunity to add protection from elongated solid andjet-like projectiles. As disclosed above in the background section thereare systems having two layers of armor with an electrical conductordisposed therebetween. An significant electric potential is createdbetween the electrical conductor and the adjacent surfaces of the armor.When a jet or elongated solid penetrator penetrates the armor it createsan electrically conductive path between the armor layers and theelectrical conductor through which the electrical potential isdischarged. When there is sufficient electrical energy dischargedthrough the penetrator it is melted or vaporized and its ability topenetrate the next layer of armor is significantly reduced. Because sucha system can be readily incorporated into the present invention withoutsignificant disadvantage a preferred embodiment of the present inventionincludes an electrically conductive member disposed in the dispersionspace between two adjacent armor plates.

As here embodied and depicted in FIG. 9, a source of electrical power 52is disposed to apply electrical power to the electrically conductivemember 54 while the two adjacent electrically conductive armor platesare grounded. In such an embodiment the electrical power applied to theelectrically conductive member 54 poses no threat of electric shock topersonnel contacting the outer conductive armor plate, here embodied asouter armor plate 12. In this embodiment interior armor plate 14 is alsogrounded so that an elongated penetrator in electrical contact with theelectrically conductive member 54 and the interior armor plate 14 isalso subjected to electrical power to degrade the penetratortherebetween. The presence of the fibrous sheet armor 12′, an electricaland thermal insulator further improves the performance of the system byreducing the dissipation of both heat and electrical energy from thesurface of the penetrator. By confining the heat and electrical energyapplied to the penetrator within it, the energy more effectivelydegrades the penetrator. As here embodied the electrically conductivemember 54 is between plates 12 and 14 with electrical power beingapplied to the screen 54 and the armor layer 12. Alternatively, thescreen could be placed between armor layers 14 and 15 with conductivearmor layer 14 and 15 being grounded and the electrically conductivemember 54 receiving electrical power. The source of electrical powersupplies sufficient electrical power to disperse, melt, vaporize, orotherwise degrade at least a portion of an elongated projectile makingelectrical connection between at least one of the two adjacent armorplates and the electrically conductive member 54. In this embodiment thefirst dispersion space is the space 18′ because the fiber-reinforcedarmor layer 12′ does not allow dispersion of material passing throughthe fiberous material.

FIG. 10 shows another embodiment of the invention using electrical powerto enhance the performance of the armor system of the present invention.In this embodiment the electrically conductive member 54 is adjacent tothe interior surface of the fiber-reinforced sheet armor 12′. In apreferred embodiment it is adhered thereto facilitating the fabricationof this preferred armor system. In the embodiment of FIG. 10 the armorplates 12 and 14 are electrically grounded and the electrical power isapplied to the electrically conductive member 54. As with the embodimentof FIG. 9, the first dispersion space in this embodiment is the space18′ because the fiber-reinforced armor layer 12′ does not allowdispersion of material passing through the fiberous material.

FIG. 11 shows another embodiment of the invention using electrical powerto enhance the performance of the armor system of the present invention.In this embodiment the electrically conductive member 54 is adjacent toor adhered to the interior surface of the fiber-reinforced sheet armor12′. In this embodiment there is included an layer 60 comprised of anelectrical insulator. In a preferred embodiment the outer layer 60consists essentially of a ceramic material providing both electricalinsulation and advantages in defeating certain types of anti-armorprojectiles by virtue of the high compression strength of suchmaterials. The outer layer 12″ need not be armor but could include anyelectrical insulator. In the embodiment of FIG. 11 the electrical poweris applied to armor plates 12 and 14 and the electrically conductivemember 54 is electrically grounded. The presence of the outerelectrically insulating layer 12″ reduces the electrical hazard topersonnel coming in contact with the surface of the armor system. Aswith the embodiment of FIGS. 9 and 10, the first dispersion space inthis embodiment is the space 18′ because the fiber-reinforced armorlayer 12′ does not allow dispersion of material passing through thefiberous material.

FIG. 12 shows another embodiment of the invention using electrical powerto enhance the performance of the armor system of the present invention.In this embodiment the electrically conductive member 54 is adjacent toor adhered to the interior surface of the fiber-reinforced sheet armor12′. Another fiber-reinforced sheet armor 12″ is adjacent theelectrically conductive member 54 and the inner armor layer 14. Thisembodiment may include an outer layer 60 comprised of an electricalinsulator.

In a preferred embodiment the outer layer 60 consists essentially of aceramic material providing both electrical insulation and advantages indefeating certain types of anti-armor projectiles by virtue of the highcompression strength of such materials. The outer layer 60 need not bearmor but could include any electrical insulator. In the embodiment ofFIG. 12 the electrical power is applied to armor plates 12 and 14 andthe electrically conductive member 54 is electrically grounded. Thepresence of the outer electrically insulating layer 60 reduces theelectrical hazard to personnel coming in contact with the surface of thearmor system. There is no first dispersion space in this embodimentbecause the fiber-reinforced armor layers 12′ and 12″ does not allowdispersion of material passing through the fiberous material.

In the embodiments where electrical power is used to enhance theperformance of the armor system the electrical power can be applied toany conductive layer in the system with other adjacent layers beinggrounded. While configurations that apply power to the outermost layerare not preferred due to personnel hazard, such a configuration isoperable and within the scope of the invention. One skilled in the artof high energy systems can readily devise an appropriate system tosupply the requisite power to the armor systems of the presentinvention. The presence of the electrically insulating layers offiber-reinforced armor facilitate the use of such systems by providingan electrically insulative layer with a higher dielectric constant thana simple air gap. This allows the application of higher levels ofelectrical power while reducing the likelihood of electrical dischargebetween adjacent conductive layers.

In addition, the source of electrical power may be a capacitor systemconnected to adjacent conductive layers of the present invention.Moreover, the adjacent conductive layers of the armor system of thepresent invention may comprise the plates of the capacitor systemstoring the electrical energy used to defeat a projectile or penetratorpassing therethrough.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present invention. Thepresent invention includes modifications and variations of thisinvention which fall within the scope of the following claims and theirequivalents.

1. An armor system for defeating a solid projectile, said systemcomprising: an exterior rigid armor plate having an exterior surface andan interior surface; a fiber-reinforced sheet armor comprised of aplurality of fibers having an ultimate tensile strength greater than 2.5GPa bonded to form the sheet by a polymer surrounding the fibers, thesheet armor being affixed to the interior surface of the exterior armorplate; an interior armor plate disposed approximately parallel to thefiber-reinforced sheet armor and displaced therefrom to form a firstdispersion space between the fiber-reinforced sheet armor and theinterior armor plate; and an inner armor plate disposed approximatelyparallel to the interior armor plate and displaced therefrom to form asecond dispersion space between the interior armor plate and the innerarmor plate, the second dispersion space being sufficiently thick toallow significant lateral dispersion of materials passing therethrough.2. The system of claim 1 wherein the fiber in the fiber-reinforced sheetarmor sheet is bonded into sheet form with a matrix of polymer materialthat consists essentially of a material selected from the groupconsisting of: phenolic resins, epoxy resins, vinyl ester resins,polyester resins, acrylate resins, and polymethyl (meth)acrylate.
 3. Thesystem of claim 1 wherein the fiber in the fiber-reinforced sheet armorsheet consists essentially of a material selected from the groupconsisting of: poly-paraphenylene terephthalamide, stretch-oriented highmolecular weight polyethylene, stretch-oriented high molecular weightpolyester, a polymer based on pyridobisimidazole, and silicate glass. 4.The system of claim 1 wherein the fiber-reinforced sheet armor comprisesa sheet of self-bonded polymer comprised of a plurality of polymerfibers, each having an interior core and an exterior sheath, theinterior core being formed of a polymer having a higher melting pointand higher strength than a polymer forming the exterior sheath.
 5. Thesystem of claim 4 wherein the fiber-reinforced sheet armor consistsessentially of a material selected from the group consisting of:polypropylene and polyethylene.
 6. The system of claim 1 wherein theouter armor layer consists essentially of a sintered material selectedfrom the group consisting of: silicon carbide, boron carbide, alumina,and a blend of zirconia and alumina.
 7. The system of claim 1 whereinthe first dispersion space is sufficiently thick to allow significantlateral dispersion of material passing though the first dispersionspace.
 8. The system of claim 1 wherein the fiber-reinforced sheet armoris bonded to the interior armor plate.
 9. The system of claim 1including a plurality of spheres located in the second dispersion space,the spheres consisting essentially of a material selected from the groupof brittle metal, ceramic, and glass.
 10. The system of claim 9 whereinthe spheres are surrounded by a material selected from the group of: aliquid and a gel, said material having a velocity of forced shockgreater than 1,000 meters/sec.
 11. The system of claim 1 furtherincluding an electrically conductive member disposed in the dispersionspace between two adjacent electrically conductive armor plates, asource of electrical power disposed to apply electrical power to theelectrically conductive member the source of electrical power beingdisposed to supply sufficient electrical power to disperse at least aportion of an elongated projectile making electrical connection betweenat least one of the two adjacent armor plates and the electricallyconductive member.
 12. The system of claim 1 wherein at least one armorplate, having an outer surface opposite a dispersion space, includes aplurality of projections on the outer surface, the projections beingdisposed to at least partially fragment solid projectiles impinging onthe outer surface of the armor plate.
 13. The system of claim 1 whereinat least one armor plate, having an inner surface facing a dispersionspace, includes a plurality of projections on the inner surface, theprojections being disposed to disperse solid material erupting throughthe inner surface of the armor plate.
 14. The system of claim 1 whereinthe surface of the inner armor plate facing the dispersion space,includes a plurality of projections on the inner surface, theprojections being disposed to disperse solid material impinging on theouter surface of the inner armor plate.
 15. The system of claim 1wherein each of the armor plates are comprised of materials havingdifferent values for a velocity of transmission of a forced shock wavepassing therethrough.
 16. The system of claim 1 wherein the system is anassembly affixed to the exterior of an armored vehicle.
 17. The systemof claim 1, wherein the vehicle includes a body and the body includes alayer of sheet armor affixed to the interior surface of the body. 18.The system of claim 17, wherein the sheet armor affixed to the interiorsurface of the body comprises a rigid polymer/fiber composite.
 19. Thesystem of claim 18, wherein the sheet armor affixed to the interiorsurface of the body comprises a woven fabric comprised of fiber.
 20. Thesystem of claim 18, wherein the sheet armor affixed to the interiorsurface of the body comprises a woven fabric comprised of fiber and aplurality of ceramic plates.
 21. The system of claim 17, wherein thesheet armor is spaced from the interior surface to form a gap.
 22. Thesystem of claim 16, wherein the vehicle is a blast-resistant armoredland vehicle having a monocoque body comprised of sheet steel, the bodyhaving a bottom portion defining at least one V, with the apex of the Vsubstantially parallel to the centerline of the vehicle.
 23. A method ofdefeating an anti-armor projectile, the method comprising the steps of:interposing a rigid exterior armor plate as the outer layer of amulti-layer armor system; the exterior armor plate having an exteriorsurface and an interior surface; interposing a fiber-reinforced sheetarmor comprised of a plurality of fibers having an ultimate tensilestrength greater than 3GPa bonded to form the sheet by a polymersurrounding the fibers adjacent the exterior armor sheet such that anyprojectile defeating the exterior armor sheet next encounters thefiber-reinforced sheet armor; and interposing an interior armor plateapproximately parallel to the fiber-reinforced sheet armor and displacedtherefrom to form a first dispersion space between the fiber-reinforcedsheet armor and the interior armor plate.
 24. The method of claim 23,including the further step of: interposing an inner armor plateapproximately parallel to the interior armor plate and displacedtherefrom to form a second dispersion space between the interior armorplate and the inner armor plate, the second dispersion space beingsufficiently thick to allow significant lateral dispersion of materialspassing therethrough.
 25. The armor system of claim 1, wherein theinterior armor plate and the fiber-reinforced sheet armor are adjacent,and the first dispersion space is formed by a gap separating theinterior armor plate and the fiber-reinforced sheet armor.
 26. The armorsystem of claim 1, wherein the interior armor plate and thefiber-reinforced sheet armor are separated by a first distance, and thefirst dispersion space is formed by a gap spanning the first distance.